Abstract

Background

Honey bees are important pollinators of both crops and wild plants. Pesticide regimes that threaten their sustainability should therefore be assessed. As an example, evidence that the agricultural use of neonicotinoid pesticides is a cause of the recently observed declines in honey bees is examined. The aim is to define exacting demographic conditions for a detrimental factor to precipitate a population decline, and Hill's epidemiological ‘causality criteria’ are employed as a structured process for making an expert judgement about the proposition that trace dietary neonicotinoids in nectar and pollen cause population declines in honey bees.

Results

In spite of the absence of decisive experimental results, the analysis shows that, while the proposition is a substantially justified conjecture in the context of current knowledge, it is also substantially contraindicated by a wide variety of circumstantial epidemiological evidence.

Conclusion

It is concluded that dietary neonicotinoids cannot be implicated in honey bee declines, but this position is provisional because important gaps remain in current knowledge. Avenues for further investigations to resolve this longstanding uncertainty are therefore identified.

Abstract

The development of insecticides requires valid risk assessment procedures to avoid causing harm to beneficial insects and especially to pollinators such as the honeybee Apis mellifera. In addition to testing according to current guidelines designed to detect bee mortality, tests are needed to determine possible sublethal effects interfering with the animal’s vitality and behavioral performance. Several methods have been used to detect sublethal effects of different insecticides under laboratory conditions using olfactory conditioning. Furthermore, studies have been conducted on the influence insecticides have on foraging activity and homing ability which require time-consuming visual observation. We tested an experimental design using the radiofrequency identification (RFID) method to monitor the influence of sublethal doses of insecticides on individual honeybee foragers on an automated basis. With electronic readers positioned at the hive entrance and at an artificial food source, we obtained quantifiable data on honeybee foraging behavior. This enabled us to efficiently retrieve detailed information on flight parameters. We compared several groups of bees, fed simultaneously with different dosages of a tested substance. With this experimental approach we monitored the acute effects of sublethal doses of the neonicotinoids imidacloprid (0.15–6 ng/bee) and clothianidin (0.05–2 ng/bee) under field-like circumstances. At field-relevant doses for nectar and pollen no adverse effects were observed for either substance. Both substances led to a significant reduction of foraging activity and to longer foraging flights at doses of $0.5 ng/bee (clothianidin) and $1.5 ng/bee (imidacloprid) during the first three hours after treatment. This study demonstrates that the RFID-method is an effective way to record short-term alterations in foraging activity after insecticides have been administered once, orally, to individual bees. We contribute further information on the understanding of how honeybees are affected by sublethal doses of insecticides.

By studying the video footage, Dr Couvillon found that bees dancing vertically on the honeycomb made few "errors", repeating identical runs throughout the dance.

But bees dancing on the horizontal had more scattered runs.

"They have a hard time when they're dancing horizontally - the angles that they dance repeatedly are very different," Dr Couvillon told BBC Nature.

She explained that due to these errors a more holistic approach was needed to understand the message contained in horizontal dances.

Although the individual runs contained errors, an average calculated from all of the runs still provided accurate directions.

Dr Couvillon suggested that the inconsistencies could be attributed to gravity; when the bees are vertical on the comb they are aligned with the downward force but dancing horizontally requires more effort.

"If you were a rock climber and I asked you to get something to your right, at 90 degrees, it would be more difficult than getting something straight ahead of you," she explained.

The results feed into an ongoing debate in the scientific community over whether the variation in waggle dances happens because bees are communicating a general area, not a specific flower, or simply because they are trying their best in difficult circumstances.

"There's no reason why a bee would need to introduce scatter into a dance," said Dr Couvillon.

"I do think the bees are challenged but I still think they're pretty good at what they're doing."

Longevity is the art of not dying. This art in turn draws heavily on the various arts of staying well. Chronic rhinosinusitis (CRS), though not usually a life-threatening illness in itself, can not only compromise quality of life but also affect the immune system and other body systems, invite other illnesses and result in shortened lives. This blog entry cites recent research about the nature of chronic sinusitis, the frequent role of MRSA infections in CRS, the role of microbial biofilms in keeping MRSA and other sinus infections drug-resistant and, finally, how manuka honey might provide a basis for treatment for CRS.